The present invention relates to testing data packet signal transceivers, and in particular, to testing a data packet signal transceiver device under test (DUT) in the presence of signal interference from one or more other DUTs.
Many of today's electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications.
When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications.
For testing these devices following their manufacture and assembly, current wireless device test systems typically employ testing subsystems for providing test signals to each device under test (DUT) and analyzing signals received from each DUT. Some subsystems (often referred to as “testers”) include at least a vector signal generator (VSG) for providing the source signals to be transmitted to the DUT, and a vector signal analyzer (VSA) for analyzing signals produced by the DUT. The production of test signals by the VSG and signal analysis performed by the VSA are generally programmable (e.g., through use of an internal programmable controller or an external programmable controller such as a personal computer) so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless signal technology standards with differing frequency ranges, bandwidths and signal modulation characteristics.
As part of the manufacturing of wireless communication devices, one significant component of production cost is costs associated with these manufacturing tests. Typically, there is a direct correlation between the cost of test and the sophistication of the test equipment required to perform the test. Thus, innovations that can preserve test accuracy while minimizing equipment costs (e.g., increasing costs due to increasing sophistication of necessary test equipment, or testers) are important and can provide significant costs savings, particularly in view of the large numbers of such devices being manufactured and tested.
One technique being used to reduce costs and time associated with manufacturing test is to test multiple DUTs concurrently by assembling and connecting one or more testers with additional signal routing circuitry (e.g., power dividers, power combiners, signal switches, multiplexors, etc.) as needed for providing receive (RX) signals to the DUTs and for receiving and analyzing transmit (TX) signals produced by the DUTs. In such a manufacturing test environment, the testers and DUTs will all be emitting radio frequency (RF) signals, often concurrently, thereby resulting in significant likelihood of signal interference. For example, a signal from the tester intended for one DUT may be erroneously received and acted upon by another DUT. Alternatively, signals generated by multiple DUTs may interfere with one another, as well as cause the tester to erroneously identify such signals as valid or invalid when, in fact, the opposite is true, notwithstanding the use of various signal shielding mechanisms to keep such signals mutually isolated.
For example, when interference by a signal to or from one DUT causes a data packet signal received by a second DUT to be identified as “bad”, that second DUT will indicate a packet error. However, such an error indication would be a false negative caused by the interfering packet, thereby causing the measured packet error rate (PER) to appear higher than the actual PER. In the event that the measured PER becomes high enough to cause the test to fail, it is then generally necessary for the test system to repeat the test, or identify the DUT as defective. However, due to the interference, such a measured PER is inaccurate and not truly indicative of a problem with the DUT. Accordingly, the repetition of the test is unnecessary and introduces additional testing costs due to the time needed to repeat the test, or introduces even greater costs by erroneously identifying the DUT as defective.
Accordingly, it would be desirable to be able to detect instances of signal interference in real time and take simple remedial steps to prevent inaccurate test measurements that otherwise would result in prolonged and unnecessarily repeated testing, and erroneous identifications of DUTs as defective.